Split all the e2e tests in their own files

Some duplication is avoided, but most importantly: it’s much much cleaner,
easier to find, functions have been cleaned up (functools.partial usages are
now hidden), etc.

tests/end_to_end/scenarios/execute_hello_adhoc_command.py

@@ -0,0 +1,15 @@
+from scenarios import *
+
+scenario = (
+    sequences.handshake(),
+    send_stanza("<iq type='set' id='hello-command1' from='{jid_one}/{resource_one}' to='{biboumi_host}'><command xmlns='http://jabber.org/protocol/commands' node='hello' action='execute' /></iq>"),
+    expect_stanza("/iq[@type='result']/commands:command[@node='hello'][@sessionid][@status='executing']",
+                  "/iq/commands:command/dataform:x[@type='form']/dataform:title[text()='Configure your name.']",
+                  "/iq/commands:command/dataform:x[@type='form']/dataform:instructions[text()='Please provide your name.']",
+                  "/iq/commands:command/dataform:x[@type='form']/dataform:field[@type='text-single']/dataform:required",
+                  "/iq/commands:command/commands:actions/commands:complete",
+                  after = save_value("sessionid", extract_attribute("/iq[@type='result']/commands:command[@node='hello']", "sessionid"))
+                  ),
+    send_stanza("<iq type='set' id='hello-command2' from='{jid_one}/{resource_one}' to='{biboumi_host}'><command xmlns='http://jabber.org/protocol/commands' node='hello' sessionid='{sessionid}' action='complete'><x xmlns='jabber:x:data' type='submit'><field var='name'><value>COUCOU</value></field></x></command></iq>"),
+    expect_stanza("/iq[@type='result']/commands:command[@node='hello'][@status='completed']/commands:note[@type='info'][text()='Hello COUCOU!']")
+)